Windshears are dangerous phenomena for an aircraft, in particular during the landing and takeoff phases where the margin for maneuver in relation to the terrain is all the smaller the stronger the wind currents. To forestall dramatic changes of speed and altitude, reactive systems for detecting windshear conditions exist. Nevertheless, certain turbulence and gusts that may be encountered by an aircraft in the course of an approach or takeoff phase possess frequencies and/or amplitudes that the reactive windshear detection system might interpret as belonging to the group of windshears and thus leading to the generation of a false alarm.
In the field of aeronautics, reactive embedded windshear detection systems remain sensitive to the atmospheric conditions whose properties are close to those of windshears. In particular, the reactive systems which process the filtered data arising from the airplane sensors are sensitive to gusts and turbulence.
According to the known art, reactive windshear detection systems limit the number of false alarms by spectrally filtering the data arising directly from the sensors: angles of attack, accelerations, roll, yaw and pitch. However, turbulence and gusts exist in a wide range of frequencies and the number of residual false alarms does not satisfy the values expected by the standards and feedback in commercial operations.
The invention is aimed at alleviating the problems cited above by proposing a method and device for filtering alarms originating from a system for detecting windshears. The invention has the advantage of reducing the number of false alarms in the presence of gusts or turbulence. The invention is based on processing the second derivative with respect to time of the angle of attack of the aircraft as well as the second derivative of the estimated severity factor. The invention furthermore makes it possible to analyze in parallel the calculated values of the vertical wind and of the horizontal deceleration or acceleration and to compare them with aircraft-dependent threshold values. Thus, the invention makes it possible to differentiate genuine windshear from a gust or turbulence and consequently to avoid the emission of false alarms.
The invention also has the advantage of being able to operate with any system for detecting windshears. Specifically the invention implements an additional filter compatible with the detection systems according to the known art.